Merge tag 'for-linus-v3.7-rc5' of git://oss.sgi.com/xfs/xfs

Pull xfs bugfixes from Ben Myers:

 - fix for large transactions spanning multiple iclog buffers

 - zero the allocation_args structure on the stack before using it to
   determine whether to use a worker for allocation
 - move allocation stack switch to xfs_bmapi_allocate in order to
   prevent deadlock on AGF buffers

 - growfs no longer reads in garbage for new secondary superblocks

 - silence a build warning

 - ensure that invalid buffers never get written to disk while on free
   list

 - don't vmap inode cluster buffers during free

 - fix buffer shutdown reference count mismatch

 - fix reading of wrapped log data

* tag 'for-linus-v3.7-rc5' of git://oss.sgi.com/xfs/xfs:
  xfs: fix reading of wrapped log data
  xfs: fix buffer shudown reference count mismatch
  xfs: don't vmap inode cluster buffers during free
  xfs: invalidate allocbt blocks moved to the free list
  xfs: silence uninitialised f.file warning.
  xfs: growfs: don't read garbage for new secondary superblocks
  xfs: move allocation stack switch up to xfs_bmapi_allocate
  xfs: introduce XFS_BMAPI_STACK_SWITCH
  xfs: zero allocation_args on the kernel stack
  xfs: only update the last_sync_lsn when a transaction completes

1 files changed, 18 insertions, 0 deletions

diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index a8d0ed9..becf4a9 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -526,7 +526,25 @@ xfs_buf_item_unpin(
 		}
 		xfs_buf_relse(bp);
 	} else if (freed && remove) {
+		/*
+		 * There are currently two references to the buffer - the active
+		 * LRU reference and the buf log item. What we are about to do
+		 * here - simulate a failed IO completion - requires 3
+		 * references.
+		 *
+		 * The LRU reference is removed by the xfs_buf_stale() call. The
+		 * buf item reference is removed by the xfs_buf_iodone()
+		 * callback that is run by xfs_buf_do_callbacks() during ioend
+		 * processing (via the bp->b_iodone callback), and then finally
+		 * the ioend processing will drop the IO reference if the buffer
+		 * is marked XBF_ASYNC.
+		 *
+		 * Hence we need to take an additional reference here so that IO
+		 * completion processing doesn't free the buffer prematurely.
+		 */
 		xfs_buf_lock(bp);
+		xfs_buf_hold(bp);
+		bp->b_flags |= XBF_ASYNC;
 		xfs_buf_ioerror(bp, EIO);
 		XFS_BUF_UNDONE(bp);
 		xfs_buf_stale(bp);